Cheesy Low-Carb Tuna Casserole

Name: Cheesy Low-Carb Tuna Casserole
Prep time: 10 min
Cook time: 15 min
Total time: 25 min
Ingredients: ½ head broccoli (200 g/ 7.1 oz); ½ head small cauliflower (200 g/ 7.1 oz); 1 large can of tuna, drained (375 g/ 13.2 oz); 1 recipe Keto Cheese Sauce (makes about 1 cup/ 240 ml); ¾ grated mozzarella cheese or cheddar (85 g/ 3 oz)

Dearna BondUpdated 5 October 2026★★★★★4.6 (198 ratings)

Ready in 25m
5.8 g net carbs
342 kcal
Serves 4

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Cheesy Low-Carb Tuna Casserole (gluten-free, keto, grain-free)

Comfort food for my partner is anything hot and cheesy, but eating too much of it can feel heavy. This keto casserole strikes the perfect balance, combining a creamy, cheesy sauce with low-carb vegetables and canned tuna. It’s hearty without being overly rich, making it a go-to dinner for us.

This recipe makes 4 regular servings or 2 to 3 larger portions, especially if you follow a higher-protein keto diet. Enjoy!

Why This Recipe Is Perfect for Keto

Perfect for Meal Prep: It’s freezer-friendly and stays fresh in the fridge for up to five days.
Ideal for Busy Weeknights: Minimal prep and just 20 minutes of cooking time. Naturally Low-Carb and High in Protein: Great for keto diets or anyone looking to cut carbs.
Budget-Friendly: Uses affordable pantry staples like canned tuna and simple veggies.
Quick and Easy: Made with common ingredients you probably already have on hand.

Key Ingredients & Swaps

Here’s a breakdown of the key ingredients for this casserole, along with some easy swaps to suit your preferences:

Broccoli and Cauliflower: These are great low-carb options, but you can easily swap them for zucchini, spinach, green beans, or even bell peppers. Frozen veggies work just as well—just thaw and drain them before using.
Canned Tuna: A budget-friendly and high-protein choice. If you prefer other options, try canned or smoked salmon, mackerel, or sardines. Not a fan of fish? Use shredded rotisserie chicken or leftover cooked turkey instead.
Keto Cheese Sauce: The star of the dish, this creamy sauce ties everything together. You can stick with the classic Keto Cheese Sauce, or try other options like Herb Cheese Sauce for a fresh, herby twist, or Blue Cheese Sauce for a bolder flavor.
Grated Cheese: Mozzarella or cheddar works well for that melty top layer, but feel free to experiment with other types like gouda or Monterey Jack.

Tips for Making the Perfect Cheesy Tuna Casserole

To make sure your cheesy low-carb tuna casserole turns out just right, keep these tips in mind:

Don’t Overcook the Veggies: Steam the broccoli and cauliflower until just tender to avoid them getting mushy in the oven.
Drain the Tuna Well: Excess liquid can make the casserole watery, so be sure to drain the canned tuna thoroughly.
Mix the Ingredients Gently: When combining the cheese sauce with the veggies and tuna, gently fold them together to keep the veggies from breaking apart.
Use an Ovenproof Dish: Pick a dish that can go from prep to baking and is large enough to hold all the ingredients comfortably.
Check for Bubbling Cheese: The casserole is done when the cheese is golden and bubbling on top, which usually takes around 15 minutes.

Storage Tips

To store leftovers, let the casserole cool completely before transferring it to an airtight container. It will stay fresh in the fridge for up to five days. If you want to freeze it, you can do so in individual portions or as a whole in a freezer-safe container for up to three months. Just remember to thaw it in the fridge overnight before reheating.

When it’s time to reheat, the best way is to pop it in the oven at 350°F (175°C) for about 10-15 minutes until heated through. This helps maintain the crispy cheese topping. If you’re in a hurry, you can microwave individual portions, but you may lose some of that nice, cheesy texture.

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Step-by-step

Preheat oven to 180 °C/ 355 °F (conventional), or 160 °C/ 320 °F (fan assisted).
Chop the broccoli and cauliflower into small florets and steam until just tender. Set aside to cool slightly. If you're using frozen and thawed vegetables, you won't have to cook them.
Add the vegetables and tuna to a large ovenproof dish and pour over the sauce, then gently stir through.
Sprinkle with the cheese.
Bake 15 minutes or until golden on top.
Serve or let it cool down and store in the fridge up to 5 days. Reheat before serving.

Recipe